Field of the Disclosure
The present disclosure relates to the field of surveillance cameras for safety and security applications. A surveillance apparatus, having an optical camera and an additional radar sensor, and a corresponding surveillance method are disclosed. Application scenarios include burglar, theft or intruder alarm as well as monitoring public and private areas.
Description of Related Art
Optical surveillance cameras are used in many public places such as train stations, stadiums, supermarkets and airports to prevent crimes or to identify criminals after they committed a crime. Optical surveillance cameras are widely used in retail stores for video surveillance. Other important applications are safety-related applications including the monitoring of hallways, doors, entrance areas and exits for example emergency exits.
While optical surveillance cameras show very good performance under regular operating conditions, these systems are prone to visual impairments. In particular, the images of optical surveillance cameras are impaired by smoke, dust, fog, fire and the like. Furthermore, a sufficient amount of ambient light or an additional artificial light source is required, for example at night.
An optical surveillance camera is also vulnerable to attacks of the optical system, for example paint from a spray attack, stickers glued to the optical system, cardboard or paper obstructing the field of view, or simply a photograph that pretends that the expected scene is monitored. Furthermore, the optical system can be attacked by laser pointers, by blinding the camera or by mechanical repositioning of the optical system.
In addition to imaging a scenery, it can be advantageous to obtain information about the distance to an object or position of an object or a person in the monitored scenery. A three-dimensional image of a scenery can be obtained, for example, with a stereoscopic camera system. However, this requires proper calibration of the optical surveillance cameras which is very complex, time consuming, and expensive. Furthermore a stereoscopic camera system typically is significantly larger and more expensive compared to a monocular, single camera setup.
In a completely different technological field, automotive driver assistance systems, US 2011/0163904 A1 discloses an integrated radar-camera sensor for enhanced vehicle safety. The radar sensor and the camera are rigidly fixed with respect to each other and have a substantially identical, limited field of view.
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor(s), to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure.